My children went to playgroup 20 years ago. It was a church hall, with around 20 children aged from 2.5 up to school age and lots of mature lady helpers. The helpers were paid, and it wasn't allied to the church as such, but I don't think it was really a profit-making thing either; they just wanted to cover costs and salaries. I think it was around £10 per session, but mostly covered by free childcare for over 3s.
They played a lot, did a little bit of more structured education, did painting and crafts, sometimes cooking eg sandwiches, cake decorating, listened to stories, sang songs and learned independence skills such as going to the loo and putting their own coats on.
It was just two and a half hours, mornings only and you had to be out for nappies before you could join. Parents didn't stay.
Children of working parents were often dropped off and picked up by their childminders. My children went three mornings a week but some did all five.
(There were also mum and baby groups, or toddlers groups, which were open from birth to school age, they were only £1 or two, but run by volunteers, and parents stayed with their children and drank tea while the children played. Usually there would be a sing-song at the end.)